Chinese hamster ovary cell

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CHO cells adhered to a surface, seen under phase-contrast microscopy

Chinese hamster ovary (CHO) cells are an epithelial cell line derived from the ovary of the Chinese hamster, often used in biological and medical research and commercially in the production of recombinant therapeutic proteins.[1] They have found wide use in studies of genetics, toxicity screening, nutrition and gene expression, particularly to express recombinant proteins. CHO cells are the most commonly used mammalian hosts for industrial production of recombinant protein therapeutics.[1]


Chinese hamsters had been used in research since 1919, where they were used in place of mice for typing pneumococci. They were subsequently found to be excellent vectors for transmission of kala-azar (visceral leishmaniasis), facilitating Leishmania research.[2][3]

In 1948, the Chinese hamster was first used in the United States for breeding in research laboratories. In 1957, Theodore T. Puck obtained a female Chinese hamster from Dr. George Yerganian's laboratory at the Boston Cancer Research Foundation and used it to derive the original Chinese hamster ovary (CHO) cell line. Since then, CHO cells have been a cell line of choice because of their rapid growth in suspension culture and high protein production.[2][4]

The thrombolytic medication alteplase (Activase), which was approved by the US Food and Drug Administration in 1987, was the first commercially available recombinant protein produced from CHO cells.[2][5] CHO cells have played a significant role in the production of recombinant protein therapeutics since, with CHO cells producing 70% of biologics and monoclonal antibodies in 2016.[6][7]


All CHO cell lines are deficient in proline synthesis.[8] Also, CHO cells do not express the epidermal growth factor receptor (EGFR), which makes them ideal in the investigation of various EGFR mutations.[9]

Furthermore, Chinese hamster ovary cells are able to produce proteins with complex glycosylations, post-translational modifications (PTMs) similar to those produced in humans. They are easily growable in large-scale cultures and have great viability, which is why they are ideal for GMP protein production. Also, CHO cells are tolerant to variations in parameters, be it oxygen levels, pH-value, temperature or cell density.[10]

Having a very low chromosome number (2n=22) for a mammal, the Chinese hamster is also a good model for radiation cytogenetics and tissue culture.[11]


Since the original CHO cell line was described in 1956, many variants of the cell line have been developed for various purposes.[8] In 1957, CHO-K1 was generated from a single clone of CHO cells.[12] Variants of K1 include the deposits in ATCC, ECACC, and a version adated for growth in protein-free medium.[12]

CHO-K1 was mutagenized in the 1970s with ethyl methanesulfonate to generate a cell line lacking dihydrofolate reductase (DHFR) activity, referred to as CHO-DXB11 (also referred to as CHO-DUKX).[13] However, these cells, when mutagenized, could revert to DHFR activity, making their utility for research somewhat limited.[13] Subsequently in 1983, CHO cells were mutagenized with gamma radiation to yield a cell line in which both alleles of the DHFR locus were completely eliminated, termed CHO-DG44.[14] These DHFR-deficient strains require glycine, hypoxanthine, and thymidine for growth.[14] Cell lines with mutated DHFR are useful for genetic manipulation as cells transfected with a gene of interest along with a functional copy of the DHFR gene can easily be screened for in thymidine-lacking media. Due to this, CHO cells lacking DHFR are the most widely used CHO cells for industrial protein production.

More recently, other selection systems have become popular and with vector systems that can more efficiently target active chromatin in CHO cells, antibiotic selection (puromycin) can be used as well to generate recombinant cells expressing proteins at high level. This sort of system requires no special mutation, so that non-DHFR-deficient host cell culture have been found to produce excellent levels of proteins.

Since CHO cells have a very high propensity of genetic instability (like all immortalised cells) one should not assume that the names applied indicate their usefulness for manufacturing purposes. For example, the three K1 offspring cultures available in 2013 each have significant accumulated mutations compared to each other.[12] Most, if not all industrially used CHO cell lines are now cultivated in animal component free media or in chemically defined media, and are used in large scale bioreactors under suspension culture.[8][12] The complex genetics of CHO cells and the issues concerning clonal derivation of cell population was extensively discussed.[15][16]

Genetic manipulation[edit]

Much of the genetic manipulation done in CHO cells is done in cells lacking DHFR enzyme. This genetic selection scheme remains one of the standard methods to establish transfected CHO cell lines for the production of recombinant therapeutic proteins. The process begins with the molecular cloning of the gene of interest and the DHFR gene into a single mammalian expression system. The plasmid DNA carrying the two genes is then transfected into cells, and the cells are grown under selective conditions in a thymidine-lacking medium. Surviving cells will have the exogenous DHFR gene along with the gene of interest integrated in its genome.[17][18] The growth rate and the level of recombinant protein production of each cell line varies widely. To obtain a few stably transfected cell lines with the desired phenotypic characteristics, evaluating several hundred candidate cell lines may be necessary.

The CHO and CHO-K1 cell lines can be obtained from a number of biological resource centres such as the European Collection of Cell Cultures, which is part of the Health Protection Agency Culture Collections. These organizations also maintain data, such as growth curves, timelapse videos of growth, images, and subculture routine information.[19]

Industrial use[edit]

CHO cells are the most common mammalian cell line used for mass production of therapeutic proteins.[1] They can produce recombinant protein on the scale of 3–10 grams per liter of culture.[8] Products of CHO cells are suitable for human applications, as they allow post-translational modifications to recombinant proteins which can function in humans.[20]

See also[edit]


  1. ^ a b c Wurm FM (2004). "Production of recombinant protein therapeutics in cultivated mammalian cells". Nature Biotechnology. 22 (11): 1393–1398. doi:10.1038/nbt1026. PMID 15529164. S2CID 20428452.
  2. ^ a b c "Vital Tools A Brief History of CHO Cells" (PDF). LSF Magazine. Winter 2015. pp. 38–47. Retrieved 5 April 2023.
  3. ^ Young C, Smyly H, Brown C (March 1924). "Experimental kala-azar in a hamster". Experimental Biology and Medicine. 21 (6): 357–359. doi:10.3181/00379727-21-182. ISSN 1535-3702.
  4. ^ Fanelli, Alex (2016). "CHO Cells". Retrieved 28 November 2017.
  5. ^ Du C; Webb C (2011). "Cellular Systems". Comprehensive Biotechnology. Elsevier. pp. 11–23. doi:10.1016/b978-0-08-088504-9.00080-5. ISBN 9780080885049.
  6. ^ Tihanyi B, Nyitray L (December 2020). "Recent advances in CHO cell line development for recombinant protein production". Drug Discovery Today. 38: 25–34. doi:10.1016/j.ddtec.2021.02.003. hdl:10831/82853. PMID 34895638. However, 70% of biologics, and almost all mAbs, are produced in Chinese hamster ovary (CHO) cells, as the most commonly used and preferred hosts for biopharmaceutical protein production.
  7. ^ Liang K, Luo H, Li Q (2023). "Enhancing and stabilizing monoclonal antibody production by Chinese hamster ovary (CHO) cells with optimized perfusion culture strategies". Frontiers in Bioengineering and Biotechnology. 11: 1112349. doi:10.3389/fbioe.2023.1112349. PMC 9895834. PMID 36741761. Since 2016, about 70% of all rBPs and mAbs were produced from Chinese hamster ovary (CHO) cell lines
  8. ^ a b c d Wurm FM; Hacker D (2011). "First CHO genome". Nature Biotechnology. 29 (8): 718–20. doi:10.1038/nbt.1943. PMID 21822249. S2CID 8422581.
  9. ^ Ahsan, A.; S. M. Hiniker; M. A. Davis; T. S. Lawrence; M. K. Nyati (2009). "Role of Cell Cycle in Epidermal Growth Factor Receptor Inhibitor-Mediated Radiosensitization". Cancer Research. 69 (12): 5108–5114. doi:10.1158/0008-5472.CAN-09-0466. PMC 2697971. PMID 19509222.
  10. ^ "CHO cells - 7 facts about the cell line derived from the ovary of the Chinese hamster". evitria AG. 3 May 2022.
  11. ^ Tjio J. H.; Puck T. T. (1958). "Genetics of somatic mammalian cells. II. chromosomal constitution of cells in tissue culture". J. Exp. Med. 108 (2): 259–271. doi:10.1084/jem.108.2.259. PMC 2136870. PMID 13563760.
  12. ^ a b c d Lewis NE; Liu X; Li Y; Nagarajan H; Yerganian G; O'Brien E; et al. (2013). "Genomic landscapes of Chinese hamster ovary cell lines as revealed by the Cricetulus griseus draft genome". Nature Biotechnology. 31 (8): 759–765. doi:10.1038/nbt.2624. PMID 23873082.
  13. ^ a b Urlaub G; Chasin LA (July 1980). "Isolation of Chinese hamster cell mutants deficient in dihydrofolate reductase activity". Proceedings of the National Academy of Sciences of the United States of America. 77 (7): 4216–4220. Bibcode:1980PNAS...77.4216U. doi:10.1073/pnas.77.7.4216. PMC 349802. PMID 6933469.
  14. ^ a b Urlaub G; Kas E; Carothers AD; Chasin LA (June 1983). "Deletion of the diploid dihydrofolate reductase locus from cultured mammalian cells". Cell. 33 (2): 405–412. doi:10.1016/0092-8674(83)90422-1. PMID 6305508.
  15. ^ Wurm, Florian; Wurm, Maria (2017). "Cloning of CHO cells, productivity and genetic stability – a discussion". Processes. 5 (4): 20. doi:10.3390/pr5020020.
  16. ^ Reinhart, D; Damjanovic, L; Kaisermayer, C; Sommeregger, W; Gili, A; Gasselhuber, B; Castan, A; Mayrhofer, P; Grünwald-Gruber, C; Kunert, R (March 2019). "Bioprocessing of Recombinant CHO-K1, CHO-DG44, and CHO-S: CHO Expression Hosts Favor Either mAb Production or Biomass Synthesis". Biotechnology Journal. 14 (3): e1700686. doi:10.1002/biot.201700686. PMID 29701329. S2CID 13844297.
  17. ^ Lee F; Mulligan R; Berg P; Ringold G (19 November 1981). "Glucocorticoids regulate expression of dihydrofolate reductase cDNA in mouse mammary tumour virus chimaeric plasmids". Nature. 294 (5838): 228–232. Bibcode:1981Natur.294..228L. doi:10.1038/294228a0. PMID 6272123. S2CID 2501119.
  18. ^ Kaufman RJ; Sharp PA (25 August 1982). "Amplification and expression of sequences cotransfected with a modular dihydrofolate reductase complementary DNA gene". Journal of Molecular Biology. 159 (4): 601–621. doi:10.1016/0022-2836(82)90103-6. PMID 6292436.
  19. ^ "General Cell Collection: CHO-K1". 2000-01-01. Retrieved 2013-05-21.
  20. ^ Tingfeng, Lai; et al. (2013). "Advances in Mammalian Cell Line Development Technologies for Recombinant Protein Production". Pharmaceuticals. 6 (5): 579–603. doi:10.3390/ph6050579. PMC 3817724. PMID 24276168.

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